The lake is fed principally by the Southern Ewaso Ng\'iro River ,
which rises in central Kenya, and by mineral-rich hot springs. It is
quite shallow, less than three metres (9.8 ft) deep, and varies in
width depending on its water level. The lake is a maximum of 57
kilometres (35 mi) long and 22 kilometres (14 mi) wide. The
surrounding area receives irregular seasonal rainfall, mainly between
December and May totalling 800 millimetres (31 in) per year.
Temperatures at the lake are frequently above 40 °C (104 °F).

High levels of evaporation have left behind natron (sodium carbonate
decahydrate) and trona (sodium sesquicarbonate dihydrate). The
alkalinity of the lake can reach a pH of greater than 12. The
surrounding bedrock is composed of alkaline, sodium-dominated trachyte
lavas that were laid down during the
PleistocenePleistocene period. The lavas
have significant amounts of carbonate but very low calcium and
magnesium levels. This has allowed the lake to concentrate into a
caustic alkaline brine.

The color of the lake is characteristic of those where very high
evaporation rates occur. As water evaporates during the dry season,
salinity levels increase to the point that salt-loving microorganisms
begin to thrive. Such halophile organisms include some cyanobacteria
that make their own food with photosynthesis as plants do. The red
accessory photosynthesizing pigment in the cyanobacteria produces the
deep reds of the open water of the lake and the orange colors of the
shallow parts of the lake. The alkali salt crust on the surface of the
lake is also often colored red or pink by the salt-loving
microorganisms that live there.

Salt marshes and freshwater wetlands around the edges of the lake do
support a variety of plants.

Most animals find the lake's high temperature (up to 60 °C) and its
high and variable salt content inhospitable. Nonetheless, Lake Natron
is home to some endemic algae , invertebrates , and birds . In the
slightly less salty water around its margins, some fish can also
survive.

The lake is the only regular breeding area in
East AfricaEast Africa for the 2.5
million lesser flamingoes , whose status of "near threatened" results
from their dependence on this one location. When salinity increases,
so do cyanobacteria , and the lake can also support more nests. These
flamingoes, the single large flock in East Africa, gather along nearby
saline lakes to feed on Spirulina (a blue-green algae with red
pigments). Lake
NatronNatron is a safe breeding location because its caustic
environment is a barrier against predators trying to reach their nests
on seasonally forming evaporite islands. Greater flamingoes also breed
on the mud flats .

The lake has inspired the poetic nature documentary The Crimson Wing:
Mystery of the Flamingos by Disneynature, for its close relationship
with the lesser flamingoes as their only regular breeding area.

Two endemic fish species, the alkaline tilapias
Alcolapia latilabris
and A. ndalalani , also thrive in the waters at the edges of the hot
spring inlets. A. alcalica is also present in the lake, but is not
endemic.

THREATS AND PRESERVATION

The area around the salt lake is not inhabited but there is some
herding and some seasonal cultivation. Threats to the salinity balance
from increased siltation influxes will come from more projected
logging in
NatronNatron watersheds and a planned hydroelectric power plant
on the Ewaso Ng'iro across the border in
KenyaKenya . Although development
plans include construction of a dike at the north end of the lake to
contain the freshwater, the threat of dilution to this breeding ground
may still be serious. There is no formal protection.

A new threat to Lake
NatronNatron is the proposed development of a soda ash
plant on its shores. The plant would pump water from the lake and
extract the sodium carbonate to convert to washing powder for export.
Accompanying the plant would be housing for over 1000 workers, and a
coal-fired power station to provide energy for the plant complex. In
addition, there is a possibility the developers may introduce a hybrid
brine shrimp to increase the efficiency of extraction. Ol Doinyo
Lengai seen from Lake
NatronNatron

According to Chris Magin, the RSPB\'s international officer for
Africa, "The chance of the lesser flamingoes continuing to breed in
the face of such mayhem are next to zero. This development will leave
lesser flamingoes in
East AfricaEast Africa facing extinction". Seventy-five
percent of the world's lesser flamingoes are born on Lake Natron.
Currently a group of more than fifty East African conservation and
environmental institutions are running a worldwide campaign to stop
the planned construction of the soda ash factory by Tata Chemicals Ltd
of Mumbai, India and National Development Corporation of Tanzania. The
group working under the umbrella name Lake
NatronNatron Consultative Group
is being co-ordinated by Ken Mwathe, Conservation Programme Manager at
BirdLife InternationalBirdLife International 's Africa Secretariat.

As per communication on June 2008, Tata Chemicals shall not proceed
with the
NatronNatron Project and further re-examination of this project
will be subject to the Ramsar Wetlands plan, which is currently under
preparation.